Chapter 6. Configuring a network bridge

Procedure

1. Create a bridge interface:

   # nmcli connection add type bridge con-name bridge0 ifname bridge0

   This command creates a bridge named bridge0, enter:

2. Display the network interfaces, and note the names of the interfaces you want to add to the bridge:

   # nmcli device status
   DEVICE  TYPE      STATE         CONNECTION
   enp7s0  ethernet  disconnected  --
   enp8s0  ethernet  disconnected  --
   bond0   bond      connected     bond0
   bond1   bond      connected     bond1
   ...

   In this example:

   • enp7s0 and enp8s0 are not configured. To use these devices as ports, add connection profiles in the next step.
   • bond0 and bond1 have existing connection profiles. To use these devices as ports, modify their profiles in the next step.

3. Assign the interfaces to the bridge.

   1. If the interfaces you want to assign to the bridge are not configured, create new connection profiles for them:

      # nmcli connection add type ethernet slave-type bridge con-name bridge0-port1 ifname enp7s0 master bridge0
      # nmcli connection add type ethernet slave-type bridge con-name bridge0-port2 ifname enp8s0 master bridge0

      These commands create profiles for enp7s0 and enp8s0, and add them to the bridge0 connection.

   2. If you want to assign an existing connection profile to the bridge:

      1. Set the master parameter of these connections to bridge0:

         # nmcli connection modify bond0 master bridge0
         # nmcli connection modify bond1 master bridge0

         These commands assign the existing connection profiles named bond0 and bond1 to the bridge0 connection.

      2. Reactivate the connections:

         # nmcli connection up bond0
         # nmcli connection up bond1

4. Configure the IPv4 settings:

   • To use this bridge device as a port of other devices, enter:

     # nmcli connection modify bridge0 ipv4.method disabled

   • To use DHCP, no action is required.

   • To set a static IPv4 address, network mask, default gateway, and DNS server to the bridge0 connection, enter:

     # nmcli connection modify bridge0 ipv4.addresses '192.0.2.1/24' ipv4.gateway '192.0.2.254' ipv4.dns '192.0.2.253' ipv4.dns-search 'example.com' ipv4.method manual

5. Configure the IPv6 settings:

   • To use this bridge device as a port of other devices, enter:

     # nmcli connection modify bridge0 ipv6.method disabled

   • To use stateless address autoconfiguration (SLAAC), no action is required.

   • To set a static IPv6 address, network mask, default gateway, and DNS server to the bridge0 connection, enter:

     # nmcli connection modify bridge0 ipv6.addresses '2001:db8:1::1/64' ipv6.gateway '2001:db8:1::fffe' ipv6.dns '2001:db8:1::fffd' ipv6.dns-search 'example.com' ipv6.method manual

6. Optional: Configure further properties of the bridge. For example, to set the Spanning Tree Protocol (STP) priority of bridge0 to 16384, enter:

   # nmcli connection modify bridge0 bridge.priority '16384'

   By default, STP is enabled.

7. Activate the connection:

   # nmcli connection up bridge0

8. Verify that the ports are connected, and the CONNECTION column displays the port’s connection name:

   # nmcli device
   DEVICE   TYPE      STATE      CONNECTION
   ...
   enp7s0   ethernet  connected  bridge0-port1
   enp8s0   ethernet  connected  bridge0-port2

   When you activate any port of the connection, NetworkManager also activates the bridge, but not the other ports of it. You can configure that Red Hat Enterprise Linux enables all ports automatically when the bridge is enabled:

   1. Enable the connection.autoconnect-slaves parameter of the bridge connection:

      # nmcli connection modify bridge0 connection.autoconnect-slaves 1

   2. Reactivate the bridge:

      # nmcli connection up bridge0

Procedure

1. Log in to the RHEL 8 web console.

   For details, see Logging in to the web console.

2. Select the Networking tab in the navigation on the left side of the screen.
3. Click Add bridge in the Interfaces section.
4. Enter the name of the bridge device you want to create.
5. Select the interfaces that should be ports of the bridge.

6. Optional: Enable the Spanning tree protocol (STP) feature to avoid bridge loops and broadcast radiation.

   
7. Click Apply.

8. By default, the bridge uses a dynamic IP address. If you want to set a static IP address:

   1. Click the name of the bridge in the Interfaces section.
   2. Click Edit next to the protocol you want to configure.
   3. Select Manual next to Addresses, and enter the IP address, prefix, and default gateway.
   4. In the DNS section, click the + button, and enter the IP address of the DNS server. Repeat this step to set multiple DNS servers.
   5. In the DNS search domains section, click the + button, and enter the search domain.

   6. If the interface requires static routes, configure them in the Routes section.

      
   7. Click Apply

Verification

1. Select the Networking tab in the navigation on the left side of the screen, and check if there is incoming and outgoing traffic on the interface:

   

Procedure

1. If you do not know the network device names on which you want configure a network bridge, display the available devices:

   # nmcli device status
   DEVICE     TYPE      STATE                   CONNECTION
   enp7s0     ethernet  unavailable             --
   enp8s0     ethernet  unavailable             --
   ...

2. Start nmtui:

   # nmtui

3. Select Edit a connection, and press Enter.
4. Press Add.
5. Select Bridge from the list of network types, and press Enter.

6. Optional: Enter a name for the NetworkManager profile to be created.

   On hosts with multiple profiles, a meaningful name makes it easier to identify the purpose of a profile.

7. Enter the bridge device name to be created into the Device field.

8. Add ports to the bridge to be created:

   1. Press Add next to the Slaves list.
   2. Select the type of the interface you want to add as port to the bridge, for example, Ethernet.
   3. Optional: Enter a name for the NetworkManager profile to be created for this bridge port.
   4. Enter the port’s device name into the Device field.

   5. Press OK to return to the window with the bridge settings.

      Figure 6.1. Adding an Ethernet device as port to a bridge

      
   6. Repeat these steps to add more ports to the bridge.

9. Depending on your environment, configure the IP address settings in the IPv4 configuration and IPv6 configuration areas accordingly. For this, press the button next to these areas, and select:

   • Disabled, if the bridge does not require an IP address.
   • Automatic, if a DHCP server or stateless address autoconfiguration (SLAAC) dynamically assigns an IP address to the bridge.

   • Manual, if the network requires static IP address settings. In this case, you must fill further fields:

     1. Press Show next to the protocol you want to configure to display additional fields.

     2. Press Add next to Addresses, and enter the IP address and the subnet mask in Classless Inter-Domain Routing (CIDR) format.

        If you do not specify a subnet mask, NetworkManager sets a /32 subnet mask for IPv4 addresses and /64 for IPv6 addresses.

     3. Enter the address of the default gateway.
     4. Press Add next to DNS servers, and enter the DNS server address.
     5. Press Add next to Search domains, and enter the DNS search domain.

   Figure 6.2. Example of a bridge connection without IP address settings

   
10. Press OK to create and automatically activate the new connection.
11. Press Back to return to the main menu.
12. Select Quit, and press Enter to close the nmtui application.

Verification

1. Use the ip utility to display the link status of Ethernet devices that are ports of a specific bridge:

   # ip link show master bridge0
   3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000
       link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff
   4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000
       link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff

2. Use the bridge utility to display the status of Ethernet devices that are ports of any bridge device:

   # bridge link show
   3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100
   4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100
   ...

   To display the status for a specific Ethernet device, use the bridge link show dev <ethernet_device_name> command.

Procedure

1. Open a terminal, and enter nm-connection-editor:

   $ nm-connection-editor

2. Click the + button to add a new connection.
3. Select the Bridge connection type, and click Create.

4. On the Bridge tab:

   1. Optional: Set the name of the bridge interface in the Interface name field.

   2. Click the Add button to create a new connection profile for a network interface and adding the profile as a port to the bridge.

      1. Select the connection type of the interface. For example, select Ethernet for a wired connection.
      2. Optional: Set a connection name for the port device.
      3. If you create a connection profile for an Ethernet device, open the Ethernet tab, and select in the Device field the network interface you want to add as a port to the bridge. If you selected a different device type, configure it accordingly.
      4. Click Save.

   3. Repeat the previous step for each interface you want to add to the bridge.

      

5. Optional: Configure further bridge settings, such as Spanning Tree Protocol (STP) options.

6. Configure the IP address settings on both the IPv4 Settings and IPv6 Settings tabs:

   • To use this bridge device as a port of other devices, set the Method field to Disabled.
   • To use DHCP, leave the Method field at its default, Automatic (DHCP).

   • To use static IP settings, set the Method field to Manual and fill the fields accordingly:

     

7. Click Save.
8. Close nm-connection-editor.

Procedure

1. Create a YAML file, for example ~/create-bridge.yml, with the following content:

   ---
   interfaces:
   - name: bridge0
     type: linux-bridge
     state: up
     ipv4:
       enabled: true
       address:
       - ip: 192.0.2.1
         prefix-length: 24
       dhcp: false
     ipv6:
       enabled: true
       address:
       - ip: 2001:db8:1::1
         prefix-length: 64
       autoconf: false
       dhcp: false
     bridge:
       options:
         stp:
           enabled: true
       port:
         - name: enp1s0
         - name: enp7s0
   - name: enp1s0
     type: ethernet
     state: up
   - name: enp7s0
     type: ethernet
     state: up
   
   routes:
     config:
     - destination: 0.0.0.0/0
       next-hop-address: 192.0.2.254
       next-hop-interface: bridge0
     - destination: ::/0
       next-hop-address: 2001:db8:1::fffe
       next-hop-interface: bridge0
   dns-resolver:
     config:
       search:
       - example.com
       server:
       - 192.0.2.200
       - 2001:db8:1::ffbb

   These settings define a network bridge with the following settings:

   • Network interfaces in the bridge: enp1s0 and enp7s0
   • Spanning Tree Protocol (STP): Enabled
   • Static IPv4 address: 192.0.2.1 with the /24 subnet mask
   • Static IPv6 address: 2001:db8:1::1 with the /64 subnet mask
   • IPv4 default gateway: 192.0.2.254
   • IPv6 default gateway: 2001:db8:1::fffe
   • IPv4 DNS server: 192.0.2.200
   • IPv6 DNS server: 2001:db8:1::ffbb
   • DNS search domain: example.com

2. Apply the settings to the system:

   # nmstatectl apply ~/create-bridge.yml

Verification

1. Display the status of the devices and connections:

   # nmcli device status
   DEVICE      TYPE      STATE      CONNECTION
   bridge0     bridge    connected  bridge0

2. Display all settings of the connection profile:

   # nmcli connection show bridge0
   connection.id:              bridge0_
   connection.uuid:            e2cc9206-75a2-4622-89cf-1252926060a9
   connection.stable-id:       --
   connection.type:            bridge
   connection.interface-name:  bridge0
   ...

3. Display the connection settings in YAML format:

   # nmstatectl show bridge0

Procedure

1. Create a playbook file, for example ~/playbook.yml, with the following content:

   ---
   - name: Configure the network
     hosts: managed-node-01.example.com
     tasks:
       - name: Bridge connection profile with two Ethernet ports
         ansible.builtin.include_role:
           name: rhel-system-roles.network
         vars:
           network_connections:
             # Bridge profile
             - name: bridge0
               type: bridge
               interface_name: bridge0
               ip:
                 dhcp4: yes
                 auto6: yes
               state: up
   
             # Port profile for the 1st Ethernet device
             - name: bridge0-port1
               interface_name: enp7s0
               type: ethernet
               controller: bridge0
               port_type: bridge
               state: up
   
             # Port profile for the 2nd Ethernet device
             - name: bridge0-port2
               interface_name: enp8s0
               type: ethernet
               controller: bridge0
               port_type: bridge
               state: up

   The settings specified in the example playbook include the following:

   type: <profile_type>

   Sets the type of the profile to create. The example playbook creates three connection profiles: One for the bridge and two for the Ethernet devices.

   dhcp4: yes

   Enables automatic IPv4 address assignment from DHCP, PPP, or similar services.

   auto6: yes

   Enables IPv6 auto-configuration. By default, NetworkManager uses Router Advertisements. If the router announces the managed flag, NetworkManager requests an IPv6 address and prefix from a DHCPv6 server.

   For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.network/README.md file on the control node.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml

Verification

1. Display the link status of Ethernet devices that are ports of a specific bridge:

   # ansible managed-node-01.example.com -m command -a 'ip link show master bridge0'
   managed-node-01.example.com | CHANGED | rc=0 >>
   3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000
       link/ether 52:54:00:62:61:0e brd ff:ff:ff:ff:ff:ff
   4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bridge0 state UP mode DEFAULT group default qlen 1000
       link/ether 52:54:00:9e:f1:ce brd ff:ff:ff:ff:ff:ff

2. Display the status of Ethernet devices that are ports of any bridge device:

   # ansible managed-node-01.example.com -m command -a 'bridge link show'
   managed-node-01.example.com | CHANGED | rc=0 >>
   3: enp7s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100
   4: enp8s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100